Reactive Compatibilization and Biaxial Stretching of Poly(glycolic Acid)/Polycaprolactone Films for High Strength, Toughness, Barrier, and Transparency

To address the brittleness (elongation <5%) of biodegradable poly(glycolic acid) (PGA), we used reactive compatibilization and simultaneous biaxial stretching for PGA/polycaprolactone (PCL) blend films. Under biaxial stretching, the dispersed PCL phase transformed from sea–island to a lamellar structure aligned parallel to the film plane, inducing two-dimensional chain orientation and enhanced crystallization. At a stretch ratio of 4 × 4, PGA crystallinity increased from 18% to 33%, the rigid amorphous fraction rose to 51%, and the mobile amorphous fraction decreased to 16%. Consequently, the film achieved a tensile strength of 110 MPa, an elongation at break of 49%, and isotropic properties. Water vapor permeability decreased by 69% and light transmittance increased from 40% to 83% compared to neat PGA. This work reveals the regulation mechanism of biaxial stretching on the processing-structure–property relationship of PGA/PCL films, offering a high-performance processing strategy for biodegradable polyester films with potential in green packaging.